1. Field of the Invention
This invention relates to a liquid crystal display panel and a method for manufacturing the same, and a liquid crystal display device.
2. Background Art
Liquid crystal display devices are used in various household electrical appliances and information terminals including television sets, personal computers, and mobile phones. A liquid crystal display panel used in the liquid crystal display device comprises a pair of glass or other substrates opposed to each other, a spacer for holding the gap (spacing) between the pair of substrates, and a liquid crystal packed in the space formed by the pair of substrates and the spacer.
If the spacer has an unnecessarily high strength, the shrinkage of the spacer cannot follow the shrinkage of the liquid crystal having a large shrinkage ratio under low-temperature environment such as at approximately −10° C. Thus the packed liquid crystal is subjected to negative pressure and is likely to generate low-temperature bubbles.
On the other hand, if the strength of the spacer is decreased, the shrinkage of the spacer under low-temperature environment is facilitated, and the generation of low-temperature bubbles can be prevented. However, if the strength is too low, the gap between the substrates is varied upon local application of an excessive load, and color unevenness is likely to occur.
Some techniques to solve the above problem have been proposed. JP-A 2002-341354(Kokai) (hereinafter referred to as Patent Document 1) discloses a technique of using two types of spacers having different heights to prevent the generation of low-temperature bubbles and to avoid color unevenness due to external force. JP-A 2003-121857(Kokai) (hereinafter referred to as Patent Document 2) discloses a technique of using two or three types of spacers having different heights and cross-sectional areas to avoid color unevenness due to external force.
In the techniques disclosed in Patent Documents 1 and 2, spacers having different heights are disposed. The substrate is supported with only the taller spacers during periods of low temperature, and is supported with the taller and shorter spacers during application of external force.
In this case, the taller spacers support the substrate both during periods of low temperature and during application of external force, and hence may undergo plastic deformation. Plastic deformation in the taller spacers results in substrate warp. This causes variation in the in-plane thickness of the liquid crystal, and may increase the possibility of color unevenness.